反射式高能電子繞射儀應用於雷射分子磊晶成長之研究

Abstract

我們利用反射式高能電子繞射儀來臨場觀測雷射分子磊晶之薄膜成 長,並且在鈦酸鍶與釔鋇銅氧薄膜的成長過程中,已順利觀測到反射電子束 強度的振盪現象,透過原子力顯微鏡的觀察,我們便可以得知反射式高能電 子繞射儀的振盪現象與表面平整度的相關性,更可藉此深入了解薄膜成長 的機制 我們發現在不同的蒸鍍條件下(如基板表面結構,基板溫度,與 雷射重覆率等)會有不同的振盪行為出現,藉由不同的長度尺度與時間尺 度,我們建構了一個簡單的薄膜成長模式來解釋這些振盪現象,另外,我們 也發現振盪現象中反射電子束的強度差呈現出指數衰減的現象,此衰減行 為亦可類比到帶阻尼的簡協振盪子 The Reflection High Energy Electron Diffraction is used to in-situlymonitor the evolution of thin film growth in our Laser MBE system. So far, wehave successfully observed the RHEED oscillations of SrTiO3 and YBa2Cu3O(7-x)thin films. With the aid of Atomic Force Microscopy, we can get the correlationbetween the RHEED oscillations and the morphology of the thin film. This would lead us to understand the growth mechanism of thin films more deeply. It is observed that the behavior of RHEED oscillations would be changed under different deposition parameters. Some length and time scales are introduced in our growth model in order to understand these phenomena. We alsofind that the intensity difference of specular electron beam is closely analogous to the dynamic behavior of the damped simple harmonic oscillator.